Darwin and Evolution Chapter 17 History of Evolutionary Thought Prior to Darwin, most people had a mindset determined by deep-seated beliefs held to be intractable truths Biology during preceding century had slowly begun to accept the idea of evolution
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Darwin and Evolution Chapter 17
History of Evolutionary Thought • Prior to Darwin, most people had a mindset determined by deep-seated beliefs held to be intractable truths • Biology during preceding century had slowly begun to accept the idea of evolution • Living things share common characteristics due to common ancestry Mader: Biology, 9th Ed.
Mid-Eighteenth Century Taxonomy was an important endeavor during mid-eighteenth century • Carolus Linnaeus • Special creation – each species has an ideal structure and function • Fixity of species – each species had a place in the scala naturae(sequential ladder of life) Mader: Biology, 9th Ed.
Mid-Eighteenth Century Count Buffon wrote 44-volume natural history describing all known plants and animals • Provided evidence of descent with modification • Influences of the environment, migration, geographical isolation, and the struggle for existence Mader: Biology, 9th Ed.
Mid-Eighteenth Century Erasmus Darwin • Suggested common descent based on: • Changes undergone by animals during development • Artificial selection by humans • The presence of vestigial organs Mader: Biology, 9th Ed.
Late Eighteenth Century George Cuvier • First to use comparative anatomy to develop a system of classification • Founded Paleontology • Proposed Catastrophism • Hypothesized local catastrophes had occurred whenever a new strata showed a new mix of fossils • After each catastrophe, a region was repopulated by species from surrounding areas. Mader: Biology, 9th Ed.
Late Eighteenth Century Lamarck • First biologist to believe evolution occurs • First to link diversity with environmental adaptation • Concluded more complex organisms are descended from less complex organisms • Inheritance of acquired characteristics (Lamarckianism) • Giraffes stretch necks and then pass on long necks to offspring Mader: Biology, 9th Ed.
Late Eighteenth Century Charles Lyell • Supported a theory that the earth was subject to slow but continuous cycles of erosion and uplift • Uniformitarianism rates and processes of change are constant Mader: Biology, 9th Ed.
Darwin’s Theory of Evolution Mader: Biology, 9th Ed.
Darwin’s Theory of Evolution • Occurrence of Descent • Darwin was not convinced of uniformitarianism, but did believe the earth was very old • Enough time for descent with modification Mader: Biology, 9th Ed.
Biogeography • Biogeography is the study of the geographic distribution of lifeforms on earth • Darwin saw how similar species in similar habitats • Reasoned related species could be modified according to the environment Mader: Biology, 9th Ed.
Galápagos Islands • Tortoises • Darwin noticed tortoise neck length varied from one island to next • Proposed that tortoise speciation on islands could be correlated with a difference in vegetation among the islands Mader: Biology, 9th Ed.
Galápagos Islands • Finches • Darwin observed different species of finches on various islands • Speculated that all the different types of finches could have descended from a single type of mainland finch Mader: Biology, 9th Ed.
Natural Selection and Adaptation • Natural selection proposed as a driving mechanism of evolution caused by environmental selection of organisms most fit to reproduce, resulting in adaptation Mader: Biology, 9th Ed.
Three Preconditions for Natural Selection • Individuals have heritable variations • Many more individuals are produced each generation than the environment can support • Some individuals have adaptive characteristics enabling increased survival and reproduction Mader: Biology, 9th Ed.
Two Consequences of Natural Selection • Increasing proportion of succeeding generations have these characteristics • Populations become adapted to their local environment Mader: Biology, 9th Ed.
Organisms Have Variations • Darwin emphasized members of a population vary in their functional, physical, and behavioral characteristics • Believed variations were essential • New variations as likely to be helpful as harmful • Heritable variations allow adaptation to the environment Mader: Biology, 9th Ed.
Variation in a Population Mader: Biology, 9th Ed.
Organisms Struggle to Exist • Malthus stressed the reproductive potential of human beings • Proposed death and famine were inevitable due to rapid population growth • Each generation has the same reproductive potential as the previous generation • Constant struggle for existence Mader: Biology, 9th Ed.
Organisms Differ in Fitness • Fitness is the relative reproductive success of an individual • Most-fit individuals capture a disproportionate amount of resources • In nature, interactions with the environment determine which members of a population reproduce to a greater degree • Artificial Selection Mader: Biology, 9th Ed.
Artificial Selection Mader: Biology, 9th Ed.
Artificial Selection in Plants Mader: Biology, 9th Ed.
Organisms Become Adapted • An adaptation is a trait that helps an organism become more suited to its environment • Product of natural selection Mader: Biology, 9th Ed.
The Evidence of Evolution • Fossil Evidence • Fossil record is the history of life recorded by remains from the past • Documents a succession of life forms from the simple to the more complex • Sometimes the fossil record is complete enough to allow a trace of the evolutionary history of an organism Mader: Biology, 9th Ed.
Transitional Fossils Mader: Biology, 9th Ed.
Biogeographical Evidence • Distributions of many plants and animals across earth consistent with hypothesis that when forms are related, they evolved in one locale and then spread to accessible regions • Marsupials Mader: Biology, 9th Ed.
Biogeography Mader: Biology, 9th Ed.
Anatomical Evidence • Darwin was able to show a common descent hypothesis offers a plausible explanation for anatomical similarities among organisms • Despite dissimilar functions, all vertebrate forelimbs contain the same sets of bones in similar ways Mader: Biology, 9th Ed.
Anatomical Evidence • Homologous Structures are anatomically similar because they are inherited from a common ancestor • Analogous Structures serve the same function, but are not constructed similarly, and do not share a common ancestor • Vestigal Structures are fully-developed anatomical structures developed in one group of organisms, but reduced, and may have no function, in similar groups Mader: Biology, 9th Ed.
Significance of Homologous Structures Mader: Biology, 9th Ed.
Significance of Developmental Similarities Mader: Biology, 9th Ed.
Biochemical Evidence • Almost all living organisms • Use the same basic biochemical molecules • Utilize same DNA triplet code • Utilize same 20 amino acids in their proteins • When the degree of similarity in DNA base sequences are compared, the data suggest common descent • When very similar, suggest recent common descent • When more different, suggest more ancient common descent Mader: Biology, 9th Ed.
Biochemical Differences Mader: Biology, 9th Ed.
Mader: Biology, 9th Ed. www.dinosauria.com/gallery/joe/joe3.html